Human Settlements Theme Report
Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Professor Peter W. Newton, CSIRO Building, Construction and Engineering, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06747 7
Liveability: environmental quality (continued)
Indoor air quality
An earlier section has dealt with personal exposure to ambient (outdoor) air pollution (discussed in Atmosphere Report). The reality is, however, that urban populations spend 96% of each day, on average, in a range of 'enclosed environments' such as the home (new, established, mobile), the workplace (non-industrial, industrial), school, shops, recreational buildings and transit vehicles.
Figure 69 demonstrates the complexity of how pollutants arise and are distributed in one of these indoor environments - a typical office building. Air pollutants are present within buildings due to three overarching sources:
- outdoor air that is used to ventilate the buildings introduces outdoor air pollutants,
- virtually all manufactured products that we construct, furnish and use within our buildings act as emission sources for a diverse range of air pollutants, often the same as those outdoors but limited in their dispersion by the enclosed nature of building environments, and
- the behaviour of occupants (e.g. smoking).
Figure 69: Primary sources of indoor air pollution in a typical office building.
Source: CSIRO Building, Construction and Engineering.
It is important to realise that outdoor pollutants will enter all types of buildings and transport. The level of indoor air pollution depends on the level of outdoor pollution, the level and type of ventilation used, and the nature of pollutant losses to indoor surfaces (e.g. ozone decays rapidly on indoor surfaces, while carbon monoxide does not decay at all). Indoor air pollutants emitted from manufactured products will add to pollution originating outdoors, to an extent depending on the level of the product emissions, their persistence over time, and the losses by ventilation or contact with indoor surfaces (Brown 1998a, 1999a, 1999b, 2000, Brown et al. 2000, Brown and Cheng 2000). It is commonly found that indoor pollutant sources, where present, dominate in their impact on indoor air quality compared to outdoor air pollutants, as shown in Table 51. The important questions therefore relate to concentrations of these pollutant sources in buildings, and how many and what sectors of the population are exposed to the pollutants at levels considered to be hazardous. National indicators for the levels of pollutants found in buildings are currently unavailable, although protocols for determining such indicators have been developed (Brown and Robinson 1997), but are yet to be applied. Questions about the impact of outdoor air pollutants need to consider those urban environments where greatest pollutant levels occur (e.g. near busy roads and city centres)-issues which are considered in the SoE Atmosphere Theme Report.
| Pollutant | Health goal ([mu]g/m 3 at 0 kPa) | Typical indoor air concentrations ([mu]g/m 3 ) | Typical outdoor air concentration ([mu]g/m 3 ) | ||
|---|---|---|---|---|---|
| New house/office | Established house | Established office | |||
| Formaldehyde | 130 (NHMRC) | 100-800 | 20-120 | 40-120 | 10-20 |
| Total VOCs | 500 (NHMRC) | 5 000-20 000 | 200-300 | 100-300 | 20-100 |
Nitrogen dioxide
|
225 (NEPM) | - - |
10-35 60-1 500 |
-- | 10-50 (300 peak) |
Fine particles (PM10)
|
50 (NEPM) | 40-60 |
>90 5-40 |
100-30010-40 | 5-30 |
| Dust mite allergens (per gram of house dust) | 2-10 (g/g (WHO) | <0.1 | 10-60 coastal <1 inland |
<2 (data limited) | <0.1 |
Sources: Brown (1996, 1997, 1998b, 2000), Mannins (2000).
The types of pollutants and their sources and concentrations in Australian buildings can be summarised as follows (after Brown 1997):
Home - formaldehyde and VOCs from new building materials in new or renovated buildings (<6 months old); formaldehyde in mobile buildings with high loading of wood-based panels; house dust mite allergen exposure from carpets and bedding (except central Australia); environmental tobacco smoke from occupants who smoke; combustion products (nitrogen dioxide, carbon monoxide, formaldehyde) from unflued gas heaters and stoves; auto-exhausts (benzene, 1,3-butadiene, respirable particles, carbon monoxide) if dwelling has an attached garage; asbestos from friable building materials, such as insulation products.
Work - formaldehyde and volatile organic compounds (VOCs) from new building materials in new or renovated buildings (<6 months old); formaldehyde in mobile buildings with high loading of wood-based panels; office equipment emissions (VOCs, ozone, respirable particles) and cleaning product residues in non-industrial workplaces and schools; auto-exhausts (benzene, 1,3-butadiene, respirable particles, carbon monoxide) if there is an enclosed carpark or if close to busy roads; Legionella bacteria associated with water cooling towers; asbestos from friable building materials such as insulation products.
Shopping - miscellaneous emissions from consumables, cooking etc.; auto-exhausts (benzene, 1,3-butadiene, respirable particles, carbon monoxide) if enclosed carpark or if close to busy roads.
Recreation buildings - environmental tobacco smoke from occupants who smoke; auto-exhausts (benzene, 1,3-butadiene, respirable particles, carbon monoxide) if there is an enclosed carpark or if close to busy roads.
Transit - auto-exhausts (benzene, 1,3-butadiene, respirable particles, carbon monoxide) if in slow-moving traffic.
The times spent in each of these environments (time budgets) can be estimated from ABS statistics (ABS 1998i). Table 52 shows that people typically spend almost all of their daily budget in enclosed environments - 96% in 1997 - and little time (4%) outdoors. This is consistent with survey findings in other developed countries.
| Environment (ABS data source in parentheses) | 1992 | 1997 | ||
|---|---|---|---|---|
| Minutes/day | Percentage of day | Minutes/day | Percentage of day | |
| Home (personal care + domestic activities + child care + voluntary work; excluding associated travel) | 775 | 54 | 820 | 57 |
| Work (employment + education; excluding associated travel) | 205 | 14 | 199 | 14 |
| Shopping (purchasing goods and services; excluding associated travel) | 30 | 2.1 | 29 | 2 |
| Recreation (social and community interaction + recreation and leisure; excluding associated travel) | 299 | 21 | 262 | 18 |
| Transit (associated travels from all items) | 70 | 5 | 73 | 5 |
| Outdoor (domestic activities-grounds and animal care + social and community interest-attending sports events + recreation and leisure-sport and outdoor activity) | 59 | 4.1 | 54 | 3.8 |
Source: ABS (1998i).
The time spent in transit - 70 minutes per day on average - is of particular concern from the perspective of exposure to auto-exhausts (benzene, 1,3-butadiene, respirable particles, carbon monoxide) when in slow-moving traffic. Duffy and Nelson (1996) found that car occupants were exposed to much greater levels of these pollutants when travelling in urban traffic. A target level for this indicator needs to consider the pollutant levels experienced, so that the population exposure distribution (pollutant level multiplied by time exposed) can be assessed and health risks can be estimated. For example, various studies have found that benzene concentrations within vehicles in urban traffic are 20-150 g/m3, which is much higher than the outdoor benzene exposure level recommended by UK Health and Safety of 3 g/m3as an annual average.
Populations sensitive to air pollutants
It is generally considered that certain sections of the population are more likely to suffer adverse health effects from air pollutants. These are:
- the very young, since their immune systems are not fully developed and since they will experience a larger body dose than adults;
- the very old, since they may be more frail and have existing illnesses (this is already an issue in air pollution research, with fine particles in urban air having been linked to mortality rates); and
- people with existing respiratory illnesses, such as asthma, emphysema, bronchitis and hayfever.
Key trends are also problematic. For example, the Australian population is ageing so that the proportion of very old people is increasing. Also, studies have shown that the prevalence of asthma in the population has increased, particularly in schoolchildren (e.g. the prevalence of a history of asthma among seven-year olds in Melbourne increased from 19.1% in 1964 to 46% in 1990, an increase of 141%). Also, Australia has the second-highest reported death rate from asthma in the world, with the death rate from 1980 to 1990 in the 0-19 age group increasing by 50% (Robertson et al. 1991).
Based on all respiratory illnesses, it is seen that approximately one-third of the population may be sensitive to air pollutants, a proportion that increased by approximately 10% between 1990 and 1995 (Table 53). Of particular concern are the incidences of long-term conditions, such as:
- the proportion of asthmatics, which is 11.3% of the total population (an increase of about 30% in the above period), and the highest occurrence of asthma in the younger population;
- the high proportion of older Australians with bronchitis and/or emphysema; and
- the large increase in sinusitis, also most common in older Australians.
| Respiratory condition | 1989-1990 | 1995 | Percentage of population age groups in 1995 | |||||
|---|---|---|---|---|---|---|---|---|
| '000s | Percentage of population | '000s | Total | <5 years |
5-14 years | 65-74 years | >75 years | |
| Hayfever | 1 753 | 10.3 | 2 515 | 13.9 | 2.0 | 8.8 | 12.2 | 11.0 |
| Asthma | 1 444 | 8.5 | 2 041 | 11.3 | 10.7 | 19.2 | 8.9 | 7.5 |
| Sinusitis | 727 | 4.3 | 1 859 | 10.3 | 1.3 | 4.9 | 11.5 | 9.1 |
| Bronchitis/emphysema | 587 | 3.5 | 778 | 4.3 | 3.0 | 2.8 | 8.8 | 10.4 |
| All respiratory conditions | 5 867 | 34.5 | 6 749 | 37.4 | 34.3 | 37.8 | 35.3 | 33.6 |
Source: ABS (1998j).
The 1995 National Health Survey also observed that asthma was more prevalent in 0 - 4 and 5 - 9 year olds from households with smokers (13% and 22%, respectively) than in household with no smokers (9% and 18%, respectively). Passive exposure to tobacco smoke has been linked to several illnesses in young children (Hill et al. 1998). For example, passive smoking is one of the major risk factors for sudden infant death syndrome; children of smokers are 60% more likely to have serious chest infections (bronchitis, croup, pneumonia), especially in the first year of life; and 9% of childhood asthma has been attributed to passive smoking.
Thus, the proportion of children living in households with smokers is a significant indicator for a population at risk from indoor air exposure to this pollutant. Over half a million children aged 0 - 4 have been estimated to fit into this category of the population at risk (data from ABS Australian Health Surveys, 1989 - 1990 and 1995).